From UPS...they can't leave it in your mailbox because it's the law that only the post office can. From my experience UPS/Fedex/DHL will leave them. However the sponsor can request a delivery signature, in which case you'd have to be there. I once had a sponser contact me via email prior to sending the affidavit and I requested that they not require a signature because i would be at work all day and noone would be home to sign for it.